A calmer galaxy can give life new opportunities even in the most uncanny conditions. We are now on a planet where the average temperature drops below -50°C, keeping water permanently frozen. But it’s still teeming with life! Past quasar activity led to an exceptional period of cosmic calm that allowed the emergence of an exotic biochemistry. On this planet, liquid ammonia adopts the role of water. A giant creature plods over the horizon encased in an armor of water ice. Here metabolism is slower due to the glacial temperatures, but smarter species have learned to heat themselves artificially and can engage in fast-paced activities.
Ammonia has been hypothesized as a biological substitute for water. At normal pressures it freezes at -78°C and boils at -33°C.